The present invention generally relates to identity cards, and particularly to those comprised of several layers and carrying, at a suitable point on one or more of the layers, information which serves to identify the cardholder. The card could have additional security markings, such as guilloche figures, as protection against forgeries.
Cards of this type in the form of identity cards, cheque cards, credit cards, pass cards or other identification papers generally comprise an identity card core, provided with data relating to the holder, made of paper or of thermoplastic films, for example of polyvinyl chloride, which are assembled in layers to give the card core. For protection in use and for security against forgeries or unauthorized alterations of the data, the card core is covered by or laminated to external transparent films.
In the prior art identity cards are produced as a fused laminate in which a card core, carrying the information, is protected by transparent films of a nature which differs from that of the cord core. West German Offenlegungsschrift No. 2,308,876 describes such an identity card consisting of a relatively thick carrier film and a thin transparent film, between which there is a special paper having internal features, such as watermarks, banknote print or the like, which serve for protection against forgeries. Differences in the thickness of the paper can be the result of the three layers being plasticized together such that the internal features are manually, mechanically and/or visually detectable through the transparent film. Further markings which serve to identify the cardholder are provided at a suitable point in this type identity card. For example, a photograph in the form of a film transparency may be inserted between the special paper and the carrier film and would be firmly bonded to the special paper. Furthermore, at any desired point on the front or rear of the identity card, a strip of special paper could be laminated or printed according to security technology, onto the outside of the plastic material, to provide a field for later signatures or other hand-written entries.
In identity cards it is primarily the card core which is provided with security markings for preventing a forgery by imitation. It is obvious that the best protection against forgeries is obtained by a combination of different security markings and a card which consists of a laminate of layers which are resistant to attempts at separating them into individual layers and hence resistant to fraudulent interference with the information and security markings applied to the layers. In West German Patent Application No. P 28 38 759.3 corresponding to copending U.S. Pat. application Ser. No. 70,737 filed Aug. 29, 1979 such a card is discussed which has a composite card core and an upper and a lower cover layer consisting of polymers which can be fused by heat to provide a laminate. Because of the identical consistency of all the layers of the laminate, once the layers are fused during lamination, it is not generally possible to separate the layers in such an identity card without destroying the security markings applied to the card core. Possible security markings include intricate line patterns, watermarks in the case of paper, photographs of the cardholder and the like. However, if, contrary to expectation, somebody were to succeed in separating the card laminate without damage to the individual layers, it would be technically easy to forge or imitate security markings of this type.